Mr. Peregrin has been sober for eight years; this will be his third year summering on the island. He pays $2,700 for his 10-week share in a house that is stocked with Diet Coke, Fresca and Smart Water.

The house of fellow nondrinkers provides a safe haven of sorts, but it is hardly designed to be a cloistered existence. On Fire Island each weekend, Mr. Peregrin said, he and some housemates hit "Middle Tea," the early evening all-out gay dance party that takes place in and around the harbor-side Pavilion nightclub, with as much ferocity as those men who drink with whom they share the dance floor. "From 8 p.m. to 10 p.m. I dance like a madman and then go home," he said. "I had my moment, I don't need to go out and chase it again."